1. Field of the Invention
The present invention relates to a display device of an active matrix driving method in which a switching element is provided in each pixel, and a driving method thereof. In particular, the invention relates to a display device in which a luminance of a light emitting element is controlled by controlling a current supplied to the light emitting element by using a switching element connected in series to the light emitting element, and a driving method thereof. More particularly, the invention relates to a display device including an element with diode characteristics as a light emitting element and a driving method thereof.
2. Description of the Related Art
A display device including a thin film transistor as a switching element and a driving method thereof are suggested. FIG. 8A shows an example of a pixel configuration thereof.
In FIG. 8A, reference numeral 105 denotes a light emitting element, 102 denotes a thin film transistor, 103 denotes a first power source line, and 104 denotes a second power source line. The light emitting element 105 includes two electrodes and emits light at a luminance according to a supplied current value of a current flowing between two electrodes. One of the two electrodes of the light emitting element 105 is referred to as a first electrode 105a while the other is referred to as a second electrode 105b. In the pixel shown in FIG. 8A, a value of a current (hereinafter referred to as a drain current) flowing between a source and drain of the thin film transistor 102 is controlled according to a potential G1 applied to a gate of the thin film transistor 102. The drain current of the thin film transistor 102 flows between the first electrode 105a and the second electrode 105b of the light emitting element 105 connected in series to the thin film transistor 102. The light emitting element emits light at a luminance according to a supplied current. In this manner, by controlling the drain current of the thin film transistor 102, the luminance of the light emitting element 105 is controlled to perform a display.
An electroluminescence element and the like can be used as the light emitting element 105. An electroluminescence element has diode characteristics to flow a current in only one direction. FIG. 8B shows the light emitting element 105 in FIG. 8A as a diode. In FIG. 8B, the first electrode 105a is an anode and the second electrode 105b is a cathode.
A display device in which a reverse bias voltage is regularly applied to the light emitting element 105 as well as a forward bias voltage is applied to the light emitting element 105 to emit light, and a driving method thereof have been suggested (see Patent Document 1).